"Climate Change: The Facts" covers the basics of climate change. It's a resource that you can use time and again in your broadcasts, social media and community outreach — such as school visits, as your calendar starts to fill up with school back in session.

As recently as the late 1980s, the idea that emissions of greenhouse gases would change the climate was still mostly theoretical. Temperatures might be warming and sea level might be rising, but if so, the signal was hidden in the noise of natural variability. Starting around 1990, these and other signals of a changing climate emerged and they’ve gotten stronger ever since.

The warming trend does not always follow an unbroken line upward, but over decades, the trend is clear. Between the recorded data, the underlying scientific theory, the study of ancient climate, and the projected future of climate models, the big picture shows that anthropogenic climate change is happening.

This week’s Climate Matters is a quick, illustrated guide to the basics of climate change — from the atmospheric chemistry of greenhouse gases to the observed changes in numerous climate indicators to the reasons we know the warming is not just a normal climate cycle. We’ve also included references to authoritative sources, so when you cite “Climate Change: The Facts,” you know just where those facts came from.